What is the stimulus for the knee jerk reflex?

Answer 1

monosynpatic relex

Answer 2

Striking the patellar tendon with a tendon hammer just below the patella stretches the muscle spindle in the quadriceps femoris muscle. This produces a signal which travels back to the spinal cord and synapses (without interneurons) at the level of L4 in the spinal cord, completely independent of higher centres. From there, an alpha-motor neuron conducts an efferent impulse back to the quadriceps femoris muscle, triggering contraction. This contraction, coordinated with the relaxation of the antagonistic flexor hamstring muscle causes the leg to kick. This reflex is a reflex of proprioception which helps maintain posture and balance, allowing to keep one's balance with little effort or conscious thought.

The patellar reflex is a clinical and classic example of the monosynaptic reflex arc. There is no interneuron in the pathway leading to contraction of the quadriceps muscle. Instead the bipolar sensory neuron synapses directly on a motor neuron in the spinal cord. However, there is an inhibitory interneuron used to relax the antagonistic hamstring muscle.

Answer 3

The contact between the object and the knee x

Answer 4

The quadriceps femoris.

Answer 5

muscle spindle